Blast orifice unit for self-blasting compressed gas electric circuit-breakers

ABSTRACT

An axial blast interruption chamber for self-blasting compressed gas electric circuit-breakers, having a blast orifice unit internally shaped to provide, in the outlet direction, a conical convergent zone; a cylindrical zone having the smallest surface in comparison with the other internal zones, in which a plurality of decompression holes is located, the mouth sections of these holes being parallel to the axis of the interruption chamber; and a substantially conical divergent zone, the divergent zone having a plurality of ring-like grooves, each of which is of substantially triangular cross section with an open base disposed towards the outlet orifice of the interruption chamber; wherein the decompression holes have substantially the shape of oblique truncated cones with their axis slanting in the gas outflow direction; an external shell concentrically surrounding the interruption chamber; and a toroidal groove concentrically disposed in the shell, having a substantially triangular cross section with an open base disposed in the direction of the outlet orifice, the generatrix of the toroidal groove slanting in the gas outflow direction, the outlet sections of the decompression holes opening into the toroidal groove.

United States Patent Teijeiro [54] BLAST 0R IFICE UNIT FOR SELF-vBLASTING COMPRESSED GAS ELECTRIC CIRCUIT-BREAKERS Benito Jose Calvino Y.Teijeiro, Bergamo, Italy [73] Assignee: Magrini Fabbriche RiuniteMagrini Scarpa e Magnano M.S.M.S.p.A., Milan, Italy 22 Filed: Nov. 25,1970 [21] Appl.No.: 92,671

[72] Inventor:

[ June 6, 1972 FOREIGN PATENTS OR APPLlCATlONS Primary Examiner-RobertMacon Attomey-Stevens, Davis, Miller & Mosher ABSTRACT An axial blastinterruption chamber for self-blasting compressed gas electriccircuit-breakers, having a blast orifice unit internally shaped toprovide, in the outlet direction, a conical convergent zone; acylindrical zone having the smallest surface in comparison with theother internal zones, in which a plurality of decompression holes islocated, the mouth sections of these holes being parallel to the axis ofthe interruption chamber; and a substantially conical divergent zone,the divergent zone having a plurality of ring-like grooves, each ofwhich is of substantially triangular cross section with an open basedisposed towards the outlet orifice of the interruption chamber; whereinthe decompression holes have substantially the shape of obliquetruncated cones with their axis slanting in the gas outflow direction;an external shell concentrically surrounding the interruption chamber;and 'a toroidal groove concentrically disposed in the shell, having asubstantially triangular cross section with an open base disposed in thedirection of the outlet orifice, the generatrix of the toroidal grooveslanting in the gas outflow direction, the outlet sections of thedecompression holes opening into the toroidal groove.

7 Claims,2 Drawing Figures 1 BLAST ORIFICE UNIT FOR SELF-BLASTINGCOMPRESSED GAS ELECTRIC CIRCUIT-BREAKERS BACKGROUND OF THE INVENTION 1.Field of the Invention The object of this invention is an improved blastorifice unit for self-blasting compressed gas circuit-breakers, whichgreatly increases the performance of the interruption chambers withwhich these circuit-breakers are equipped in comparison with'the knownprior art types.

2. Description of the Prior Art Compressed gas circuit-breakers arealready well known relation:

or, after simplification:

L a where L stands for the chamber end part length stated in mm, and U,.is the circuit-breaker rated service voltage expressed in kV.

It has been found, however, that the axial blast interruption chambersso far known do not attain top performance with respect to the arcquenching gas exhaust and the protection of the parts external to thechamber against the action of the arc. This performance lack applies aswell to the displacement speed of the moving parts within the chamber onwhich'the disengagement of the moving from the fixed contact of asingle-pole circuit-breaker directly depends.

SUMMARY OF THE INVENTION An object of this invention istherefore toobtain the best possible performance of an interruption chamber forcompressed gas circuit-breakers, structurally improved with respect topresent devices and with particular reference to the interruptionchamber of the aforementioned Italian patent.

A further object of this invention is to improve the decom- A stillfurther object of this invention is to improve and accelerate theoutflow of decomposition and quenching gases through the exhaust orificeof the chamber and decreasing the whirling effects occurring in saidoutlet flow.

conical and convergent zone and a second cylindrical zone, the latterhaving the smallest surface in comparison with the other internal zones.A plurality of decompression holes is terruption chamber.

The chamber further comprises a third substantially conical anddivergent zone, the length of which is determined from theaforementioned experimental relation:

This third divergent zone includes a plurality of ring-like grooves,each of which has a substantially triangular cross secangles less thanin the cylindrical, and smaller surfaced'zone where they have theirmouth.

A concentric external shell surrounds chamber proper and has an outerdiameter with the chamber axis, an flow direction. The outlet natively,pled in close contact with the interruption chamber.

BRIEF DESCRIPTION OF TI-IE DRAWING tion will be hereinafter described indetail with reference to the attached drawing, wherein: Y

FIG. 1 schematically shows the longitudinal section of an interruptionchamber with its outward communicating holes (or decompresand theconical divergent end zone; and

FIG. 2 shows, on a larger scale, the detail of a decompression hole inthe smaller surfaced zone.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, theimproved blast orifice unit of the interruption chamber of thisinvention comprises a shell 4, made of the same material as theinterruption chamber and and consequently by arrows 7 (the A-A).

Holes 6, unlike prior art constructions, do not have their axesperpendicular to axis A-A of the interruption chamber; their shapetherefore is not the standard right truncated cone shape of the holesadopted by the known technique; on the contrary, as previously noted,they have an oblique flow axis from zone towards zone 9, the flow axisbeing therefore inclined in the gas outflow direction, towards axis A-A,by an angle a that, according to the preferred embodiment of thisinvention, ranges from 45 to 65. The holes which pass through the Wallof the interruption chamber proper have their outlet sections referencedl 1.

Further, unlike the known prior art, however, these holes do not openthrough section 1 1, directly into open air; rather they open intoannular groove or slot 16 in the shell 4. Groove 16 is disposedconcentrically to the interruption chamber, and has a substantiallytriangular cross section with an open base 12 directed in the samedirection as outlet orifice 2 of the interruption chamber; and, on thedrawing plane, basel2 also denotes the mark of the ring which is theopen air outflow section of groove 16. Groove 16 can be deemed atoroidal body generated by the substantially triangular geometricalfigure defined by sides l1, l2 and 19 in FIGS. 1 and 2, said figurebeing supposed as revolving around axis A-A of the chamber, whichconsequently becomes coincident with the tore axis. According to thisinvention, the generatrix line of the toroidal body, coincident with theside 19 and opposed, on the drawing plane, to the mark of the outletsection ll, is inclined, in the outflow direction and towards axis A-A,at an angle [3 ranging from 30 to 45.

As shown by the arrows in FIG. 2, the arrangement of the decompressionholes 6 and their particular shaping determine the flow of quenching gastherethrough. Each slanting truncated cone hole 6 directs the flow ofquenching gas along arrows 8; then the gas reaches groove 16 and at side19 strikes against the protective shield formed thereby, thus undergoinga deflection in the direction of arrows 17 substantially parallel toaxis A-A and to inner flow 7.

Several advantageous results are achieved with this arrangement. First,a regularization in the streaming of the gas flow through thedecompression holes 6 is obtained, whereby the exhaust from these holesis facilitated with a consequent quicker decompression of cylindricalzone 5; the whirl phenomena inside zone 5, in particular, and inside thewhole interruption chamber generally, is decreased to a negligibleamount.

Secondly, the final flow of the gas becomes substantially parallel toaxis A-A of the chamber and can thus join the gases exiting from outletopening or orifice 2 of the chamber without giving rise to any'whirlphenomena.

Thirdly, shell 4, and in particular, the protection shield establishedin zone 19 by this shell, prevents the hot gas (heated in consequence ofits contact with the arc) exiting from holes 6 from coming in contactwith the cylinder 20 made of bakelized paper or other suitableinsulating material. The efficient protection of cylinder 20 is in thisway obtained, thereby prolonging its operational life.

Finally, a further advantage ensuing from this invention (an advantagewholly non-existent in the devices of the known prior art) consists inobtaining a thrust which improves the opening of the circuit breaker byaccelerating the displacement of the moving part (in the direction ofarrow 18) with which moving contact 3 is jointed. In fact, the gasflowing in the direction of arrows 8, strikes side 19 and develops athrust against shell 4. The effects of this thrust can be analyzed byresolving it in two orthogonal directions, one parallel to axis A-A andthe other perpendicular thereto; the component according to the latterdirection has no effect on the movement of the chamber, since theinterruption chamber has no displacement perpendicular to axis A-A,whereas the component parallel to axis A A improves the circuit breakeropening (see arrow 18, FIG. 2).

The advantages obtained by this invention are increased by theadvantages due to the particular shape of the lower part 9 of thechamber which is provided with triangular cross-sectioned ring-likegrooves 13. In fact, resultants 15 of generation lines 14 of thedecomposition gases present a component parallel to axis A-A whichimproves both the outflow of the quenching (or deionizing) gas and thedecomposition gas.

The invention as hereinabove described, exemplified, illustrated andhereunder claimed, can be modified without going outside the scopethereof. For example, shell 4 can be extended in the outflow directionso that it surrounds (besides zones 1 and 5) not only a part but thewhole of zone 9, thus making decompression holes 6 open into groove 16,extending in a hollow having a right cross section in the form of a ringwhich coaxially surrounds the whole interruption chamber and has itsoutlet end section (equivalent to section 12) laying in the same planeas the outlet opening or orifice 2 of the chamber. Alternatively,decompression holes 6, instead of opening into annular groove 16, cancontinue on in single outflow ducts which are direct extensions of holes6 and have cross sections corresponding to the shape of holes 6 or joinin a suitable manner with their outlet sections 11. It is possible thatoutflow ducts l6:would in turn terminate with their own section 12, asshown, or continue on unchanged beyond section 12 to terminate in thesame plane as outlet orifice 2, in case the shell 4 is extended toinclude the whole of zone 9. It may be also noted that the cross sectionof outflow ducts 16 can be circular, elliptical, or have any othersuitable and convenient shape; this also applies to the cross section ofdecompression holes 6, although in regard to this point, it has beenconfirmed that the circular cross section is preferable in comparisonwith others. Also, the device contains at least two decompression holes6; the preferred embodiment employs four, displaced from each other byalthough it is considered possible to foresee more than four.

What is claimed is:

1. An axial blast interruption chamber for self-blasting compressed gaselectric circuit breakers, comprising a blast orifice unit having aconical convergent zone, a cylindrical zone, a plurality ofdecompression holes operatively associated with said cylindrical zone,the plane of the mouth sections of said holes being disposed parallel tothe axis of said interruption chamber, and a substantially conicaldivergent zone, the length of which is determined by the relation:'

said divergent zone containing a plurality of ring-like grooves havingsubstantially triangular cross sections with an open base disposed inthe direction of the outlet orifice of said interruption chamber;wherein said decompression holes have a substantially oblique truncatedcone shape 'with their axes slanting in the direction of gas outflow atan angle (a) less than 90 towards the axis of said interruption chamber;an external shall concentrically surrounding at least a portion ofsaid-interruption chamber; a toroidal groove concentrically disposed insaid shell, having a substantially triangular cross section with an openbase disposed in the direction of said outlet orifice, the generatrix ofsaid toroidal groove slanting in the direction of gas outflow at anangle (,8) less than 90 towards said chamber axis; outlet sections ofsaid decompression holes opening into said toroidal groove; said shelland said toroidal groove comprising a protective shield which completelycovers said outlet sections.

2. An interruption chamber according to claim 1, wherein said angle (a)ranges from 45 to 65.

3. An interruption chamber according to claim 1, wherein said angle (,8)ranges from 30 to 45.

4. An interruption chamber according to claim 1, wherein said shellaxially extends in said gas outflow direction and surrounds at leastsaid convergent zone, said cylindrical zone, and at least a part of saiddivergent zone, wherein said shell substantially fully shields saidoutlet sections.

5. An interruption chamber according to claim 1, further comprising atleast four decompression holes, adjacent holes having their axesdisposed substantially at right angles to one another.

6. An interruption chamber according to claim 1, wherein said shellcomprises a single unit with said interruption chamber. 5

7. Interruption chamber according to claim 1, wherein said shellcomprises at least one part distinct from and in close contact with saidinterruption chamber

1. An axial blast interruption chamber for self-blasting compressed gaselectric circuit breakers, comprising a blast orifice unit having aconical convergent zone, a cylindrical zone, a plurality ofdecompression holes operatively associated with said cylindrical zone,the planE of the mouth sections of said holes being disposed parallel tothe axis of said interruption chamber, and a substantially conicaldivergent zone, the length of which is determined by the relation: saiddivergent zone containing a plurality of ring-like grooves havingsubstantially triangular cross sections with an open base disposed inthe direction of the outlet orifice of said interruption chamber;wherein said decompression holes have a substantially oblique truncatedcone shape with their axes slanting in the direction of gas outflow atan angle ( Alpha ) less than 90* towards the axis of said interruptionchamber; an external shall concentrically surrounding at least a portionof said interruption chamber; a toroidal groove concentrically disposedin said shell, having a substantially triangular cross section with anopen base disposed in the direction of said outlet orifice, thegeneratrix of said toroidal groove slanting in the direction of gasoutflow at an angle ( Beta ) less than 90* towards said chamber axis;outlet sections of said decompression holes opening into said toroidalgroove; said shell and said toroidal groove comprising a protectiveshield which completely covers said outlet sections.
 2. An interruptionchamber according to claim 1, wherein said angle ( Alpha ) ranges from45* to 65* .
 3. An interruption chamber according to claim 1, whereinsaid angle ( Beta ) ranges from 30* to 45* .
 4. An interruption chamberaccording to claim 1, wherein said shell axially extends in said gasoutflow direction and surrounds at least said convergent zone, saidcylindrical zone, and at least a part of said divergent zone, whereinsaid shell substantially fully shields said outlet sections.
 5. Aninterruption chamber according to claim 1, further comprising at leastfour decompression holes, adjacent holes having their axes disposedsubstantially at right angles to one another.
 6. An interruption chamberaccording to claim 1, wherein said shell comprises a single unit withsaid interruption chamber.
 7. Interruption chamber according to claim 1,wherein said shell comprises at least one part distinct from and inclose contact with said interruption chamber.